In the field of photodetection some applications require exposure of the devices to bright ambient condition. One such application would by any of the systems designed to receive and/or detect laser beam or pulses in the field. That is, a laser receiver subject to sunlight exposure. Heretofore, no known system has been provided that will compensate for ambient daylight in a laser receiver. Such a system would be advantageous, and in some applications would be necessary, to avoid detector saturation. If the receiver is saturated by ambient conditions a pulse of interest received during the period of saturation cannot be detected by the receiver. As a result, important information may be lost. Therefore, if the effectiveness of a laser receiver is to be improved it must include means for preventing receiver saturation from ambient conditions.
The present invention is such a system. It senses the direct current resulting from the detector's exposure to ambient conditions and generates an equal but opposite current to counteract its effect. Thereby, the system is adapted to the conditions of its environment.
Also disclosed is a dual equalization circuit as an alternate to portions of conventional receivers to provide ultra-high system sensitivity. Increased sensitivity increases efficiency in any receiver circuit and is especially beneficial when the signal to noise ratio of the input is low, as is the case with high ambient noise levels. High noise levels are present in signals received by optical receivers exposed to bright sunlight, for example.